An fMRI study of the effect of satiation on reward and aversion

Exposure of satiated subjects to food related stimuli has been shown to decrease neural activation in areas involved in the control of eating behaviour. In the present study we investigated whether hunger or satiation affected BOLD fMRI responses to both rewarding and aversive visual and taste stimuli in healthy volunteers. Sixteen participants (8 male, 8 female) completed an fMRI task that has been used previously to assess the effects of serotonergic and dopaminergic drugs on reward processes. Participants were scanned before and after either eating to satiation or hungry (on separate test days); BOLD fMRI responses and subjective ratings, to the sight and/or taste of chocolate (rewarding) or the sight and/or taste of mouldy strawberries (aversive) were recorded. Analysis of VAS ratings of subjective pleasantness and wanting of the stimuli, suggests a dissociation between reward and aversion, as satiation attenuated responses to chocolate but not mouldy strawberries. The fMRI results showed differences in the BOLD response between the satiated and hungry conditions that were dependent on the nature of the stimuli (rewarding vs. aversive) in the following regions: orbital frontal cortex, insula, nucleus accumbens, caudate, putamen, hippocampus, amygdala and brainstem. The results provide a profile of satiation in a model of reward processing which may be of value in future studies to assess the mechanism of action of novel drugs to treat obesity and psychiatric disorders.